The devastation that Hurricane Katrina wrought on New Orleans and its surrounding communities stunned the world. Its consequences are likely to be particularly acute for adolescents, who are vulnerable for co-occurring trauma and substance abuse under conditions of extreme stress, family disorganization, and life disruption. This proposal, submitted in response to NOT-DA-05-013, "Notice of Mechanism for Time- Sensitive Research Opportunities: PAR-05-150, Expansion to Include Alcohol and Drug Abuse Research Pertaining to Hurricane Katrina," would be the first examination of the links between adolescent substance abuse and trauma following a community-wide disaster. Using this rapid review and funding opportunity, the study would explore the potential of a family-based intervention, Multidimensional Family therapy (MDFT; Liddle, 2002a), to address comorbid trauma and substance abuse among teens impacted by Hurricane Katrina. MDFT has demonstrated strong effects on adolescent substance abuse and comorbid problems, yet has not been fully tested with traumatized teens and their families. The investigators will partner with clinical providers in St. Charles Parish, Louisiana, a New Orleans area community that was heavily impacted by the storm, to rigorously test MDFT vs. group CBT in a real-world service setting. This randomized controlled trial has four aims: 1) To explore links between hurricane-related stress and trauma and youths' substance abuse; 2) To investigate in a community-based randomized controlled trial the effectiveness of a family-based intervention (MDFT) vs. group CBT for teen substance abusers impacted by Hurricane Katrina; 3) To examine teen and parent coping as mediators of treatment effects; and 4) To explore moderators of treatment effects based on post-Katrina stress and trauma symptoms. 150 youth ages 13 to 17 who are clinically referred for outpatient substance abuse treatment and experiencing trauma symptoms related to the hurricane will be randomized to either MDFT or group CBT. Both treatments will incorporate trauma-focused interventions and will be delivered by treatment providers in the same community-based agency. A multiple time point (intake, 2, 4, 6, and 12 months), multiple-domain and method assessment approach will evaluate MDFT's capacity to: (1) decrease youths' substance use, trauma, delinquency, and school problems; (2) reduce youths' diagnoses of PTSD; and (3) reduce parental stress and family conflict. Latent growth curve modeling (LGC) and parallel process LGC will be used to test study hypotheses regarding treatment outcomes, youth and parent coping as treatment mediators, and post-Katrina stress and trauma as moderators of treatment effects. The study has significant potential to advance the field by elucidating links between teen substance abuse and trauma, and validating a family-based intervention for traumatized adolescent substance abusers in the wake of the nation's most costly natural disaster. [unreadable] [unreadable] [unreadable]